This invention deals generally with x-ray tubes and more specifically with an x-ray tube which generates highly collimated radiation.
X-ray tubes function on the basis of an electron beam being generated by a cathode within the tube, and the electron beam bombarding a very small spot on an anode which is also within the tube. The bombardment of the anode, which is constructed of a suitable x-ray generating material, creates the x-rays along with a great deal of heat.
Until now most x-ray tubes have generated radiation which is poorly focused and have required secondary structures or devices to focus the beam on an object to be studied. Typical focusing structures external to the x-ray source have been spherical mirrors (U.S. Pat. No. 5,604,782 by Cash), curved crystals (U.S. Pat. 5,008,910 by Van Egeraat), capillary tubes (U.S. Pat. No. 5,001,737 by Lewis et al), and bent crystals on the inside surface of tubular structures (U.S. Pat. No. 3,898,455 by Furnas, Jr.).
A few efforts have also been made to generate a more focussed beam within the x-ray tube itself. In U.S. Pat. No. 4,352,021 by Boyd et al, multiple curvelinear anodes are disclosed, but they are also followed by a collimator structure to improve the focus. In U.S. Pat. No. 3,821,574, Burns discloses a single crystal anode of elongated channel shape which is used to generate a more intense x-ray beam because the beam is diffracted from the single crystal structure many times as it travels along the channel.
Despite this prior art, a simple structure for an x-ray tube which produces a collimated beam is not available. It would be very beneficial for both industrial and medical applications to have available an x-ray tube which is essentially interchangeable with x-ray tubes in common use but which produces a highly collimated beam which requires minimal external focusing devices.